linux-kernel - Re: linux-next: build warning in Linus' tree

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Date:	Wed, 26 May 2010 11:51:10 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Stephen Rothwell <sfr@...b.auug.org.au>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus <torvalds@...ux-foundation.org>
Subject: Re: linux-next: build warning in Linus' tree

On Wed, May 26, 2010 at 11:43:06AM +1000, Stephen Rothwell wrote:
> Hi Dave,
> 
> Today's linux-next build (x86_64 allmodconfig) produced this warning:
> 
> net/core/sock.c: In function 'sock_update_classid':
> include/net/cls_cgroup.h:42: warning: 'classid' may be used uninitialized in this function
> include/net/cls_cgroup.h:42: note: 'classid' was declared here
> 
> In the case that rcu_dereference() returns a value < 0, classid will not
> be assigned in task_cls_classid().  I don't know if this is possible - if
> not, then why is the test there?

This is a genuine bug.  I don't know why my gcc didn't warn about
it.

cls_cgroup: Initialise classid when module is absent

When the cls_cgroup module is not loaded, task_cls_classid will
return an uninitialised classid instead of zero.

Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/include/net/cls_cgroup.h b/include/net/cls_cgroup.h
index 6cf4486..726cc35 100644
--- a/include/net/cls_cgroup.h
+++ b/include/net/cls_cgroup.h
@@ -39,7 +39,7 @@ extern int net_cls_subsys_id;
 static inline u32 task_cls_classid(struct task_struct *p)
 {
 	int id;
-	u32 classid;
+	u32 classid = 0;
 
 	if (in_interrupt())
 		return 0;

Thanks,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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